System for stirring growth medium

ABSTRACT

An improved system and method for stirring suspended solids in a liquid media to enhance sample growth and improve sample detection results. The system and method employs a sample vessel holder which adapted to receive at least one sample vessel which contains the solids and liquid media and a stirrer, such as a ferrous metal filled stirrer, and maintain the sample vessel in a position such that the longitudinal axis of the sample vessel extends at an angle substantially less than 90 degrees with respect to the horizontal, such as within the range of about 15 degrees to about 25 degrees with respect to the horizontal. The system and method further employs a magnet driver, adapted to move a magnet, such as a rare earth magnet, proximate to an outer surface of the sample vessel to permit the magnet to impose a magnetic influence on the stirrer to move the stirrer in the sample vessel. Specifically, the magnet driver is adapted to move and, specifically, rotate the magnet such that the magnetic influence moves the stirrer along a side wall of the sample vessel. The magnet driver is further adapted to move the magnet away from said outer surface of the sample vessel to allow gravity to move the stirrer toward the bottom of the sample vessel. This technique therefore provides a more gentle and controlled stirring of the suspended solution.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an improved system and method forstirring suspended solids in a liquid media. More particularly, thepresent invention relates to a system and method employing a stirrer, inparticular, a magnetic ferrous metal-filled polymer, which is depositedin a vessel containing a liquid media that includes a suspended solid,and is manipulated by a moving magnet outside the vessel to stir thesuspended solid in an optimal manner.

2. Description of the Related Art

Many medical diagnoses require that a fluid sample, such as a bloodsample, be taken from a patient, cultured in a growth medium, and thenexamined for the presence of a pathogen believed to be causing thepatient's illness. The growth medium provides nutrients that allow thepathogen, such as bacteria, virus, mycobacteria, mammalian cells or thelike, to multiply to a sufficient number so that their presence can bedetected.

In some cases, the pathogen can multiply to a large enough number sothat it can be detected visually. For example, a portion of the culturecan be placed on a microscope slide, and visually examined to detect forthe presence of a pathogen of interest.

Alternatively, the presence of a pathogen or other organism can bedetected indirectly by detecting for the presence of byproducts givenoff by the microorganism during its growth. For example, certainmicroorganisms such as mammalian cells, insect cells, bacteria, viruses,mycobacteria and fungi consume oxygen during their growth and lifecycle. As the number of microorganisms increases in the sample culture,they naturally consume more oxygen. Furthermore, these oxygen consumingorganisms typically release carbon dioxide as a metabolic byproduct.Accordingly, as the number of organisms present increases, the volume ofcarbon dioxide that they collectively release likewise increases.

Alternatively, instead of detecting for the presence of carbon dioxideto detect the presence of an oxygen consuming microorganism, it ispossible to detect for a depletion in the concentration of oxygen in thesample of interest. The presence of oxygen consuming organisms can alsobe detected by detecting for a change in pressure in a sealed samplevial containing the sample of interest. That is, as oxygen in a closedsample vial is depleted by oxygen consuming organisms, the pressure inthe sealed sample vial will change. The pressure will further change inthe sample vial as the organisms emit carbon dioxide. Therefore, thepresence of such organisms can be detected by monitoring for a change inpressure in the closed sample vial.

Several methods exist for detecting the presence of carbon dioxide in asample to determine whether organisms are present in the sample. Forexample, an instrument known as the BACTEC® 9050 manufactured by BectonDickinson and Company detects for the change in color of an indicator todetermine whether carbon dioxide is present in a sample. That is, eachsample is collected in a respective sample vial containing an indicatormedium having a chemical that reacts in the presence of carbon dioxideto change color. A light sensor detects the color of the indicatormedium in the sample vial when the sample vial is loaded into theinstrument. If the sample contains an organism which emits carbondioxide, the reflected or fluorescent intensity of the indicator mediumwill change in response to the presence of carbon dioxide. The lightsensor will therefore detect this change in intensity, and theinstrument will thus indicate to an operator that an organism is presentin the sample contained in the sample vial. Other examples ofinstruments for detecting the presence of organisms in a sample bydetecting for the change in carbon dioxide in the sample are describedin U.S. Pat. Nos. 4,945,060, 5,164,796, 5,094,955 and 5,217,876, theentire contents of each of these patents are incorporated herein byreference.

An instrument employing an oxygen detecting technique is described inU.S. Pat. No. 5.567,598, the entire content of which is incorporatedherein by reference. Instruments that are capable of detecting changesin pressure in the sample vial are described in U.S. Pat. Nos.4,152,213, 5,310,658, 5,856,175 and 5,863,752, the entire contents ofeach of these patents are incorporated herein by reference. In addition,an instrument capable of detecting changes in carbon dioxideconcentration, changes in oxygen concentration, and changes in pressurein the vessel is described in a U.S. patent application of Nicholas R.Bachur et al. entitled “System and Method for Optically Monitoring theConcentration of a Gas, or the Pressure, in a Sample Vial to DetectSample Growth”, Ser. No. 09/892,061, filed on Jun. 26, 2001, and anotherinstrument capable of detecting changes in carbon dioxide concentrationor changes in oxygen concentration in the vessel is described in a U.S.patent application of Nicholas R. Bachur et al. entitled “System andMethod for Optically Monitoring the Concentration of a Gas in a SampleVial Using Photothermal Spectroscopy to Detect Sample Growth”, Ser. No.09/892,012, filed on Jun. 26, 2001, the entire contents of both of saidapplications being incorporated herein by reference.

It is noted that the results obtained by organism detection techniquesdescribed above can be improved if the growth of the organism isenhanced to cause a greater production of carbon dioxide, a greaterdepletion of oxygen, and a greater change in pressure in the vessel. Itis known that the biological activity of a solid sample in a liquidmedia can be enhanced by maintaining the solid sample in a suspendedstate. This can be accomplished by continuously stirring thesolid-liquid mixture, which improves nutrient, waste and gas exchange inthe mixture.

Examples of stirring techniques are described in U.S. Pat. Nos.5,586,823, 4,483,623 and 4,040,605, the entire contents of each areincorporated herein by reference. Each of these techniques employs amagnetic stirrer that is placed in the vessel containing the sample andmanipulated by a magnet to stir the sample in the vessel.

Although these stirring techniques may be somewhat effective inenhancing sample growth, they each suffer from certain disadvantages.For example, because each of the techniques require that the vessel bemaintained in a vertical configuration, the fluid-gas interface isminimized, especially in vessels that are not shallow. This minimalfluid-gas interface inhibits biological performance in the vessel.

In addition, the vertical configuration of the vessel allows for themagnets to lose their influence over the magnetic stirrer in the vessel,especially if the magnetic influence on the stirrer is weak as in thecase of gentle stirring. Also, the vertical configuration causes thestirrer in the vessel to follow a semi-random stirring path, whichresults in a stirring action that is inefficient and potentiallydamaging to the sample. Furthermore, in order to change the intensity ofthe stirring in these known arrangements, the physical size of thestirrer or the apparatus needs to be changed.

A need therefore exists for an improved system and method for stirringsuspended solids in a liquid media to enhance sample growth and thusimprove sample detection results.

SUMMARY OF THE INVENTION

An object of the present invention is to provide an improved system andmethod for stirring suspended solids in a liquid media to enhance samplegrowth and improve sample detection results.

Another object of the present invention is to provide an improved systemand method for stirring suspended solids in a liquid media which iscapable of changing stirring intensity without changing the size of thestirrer in the media or the size or operation of the system.

These and other objects are substantially achieved by providing a systemand method for stirring a solid suspended in a liquid in a sample vesselthat includes a stirrer, such as a ferrous material filled polymerstirrer. The system and method employs a sample vessel holder whichadapted to receive at least one sample vessel and maintain the samplevessel in a position such that the longitudinal axis of the samplevessel extends at an angle substantially less than 90 degrees withrespect to the horizontal, such as within the range of about 15 degreesto about 25 degrees with respect to the horizontal. The system andmethod further employs a magnet driver, adapted to move a magnet, suchas a rare earth magnet, proximate to an outer surface of the samplevessel to permit the magnet to impose a magnetic influence on thestirrer to move the stirrer in the sample vessel. Specifically, themagnet driver is adapted to move the magnet such that the magneticinfluence moves the stirrer along a side wall of the sample vessel. Themagnet driver is further adapted to move the magnet away from said outersurface of the sample vessel to allow gravity to move the stirrer towardthe bottom of the sample vessel. The magnet driver device can comprise amagnet shaft assembly having a magnet coupled thereto, and a motor,adapted to move the magnet shaft assembly to move the magnet proximateto the outer surface of the sample vessel and away from the outersurface of the sample vessel. The magnet shaft assembly can berotatable, and the motor rotates the magnet shaft assembly to move themagnet proximate to the outer surface of the sample vessel and away fromthe outer surface of the sample vessel. The motor can be directly ormagnetically coupled to the magnet shaft assembly. Additionally, thesample vessel holder can be adapted to receive a plurality of the samplevessels and maintain each of the sample vessels in a respective positionsuch that the longitudinal axis of each sample vessel extends at arespective angle substantially less than 90 degrees with respect to thehorizontal. Furthermore, the magnet driver can be adapted to move eachof a plurality of magnets proximate to an outer surface of a respectiveone of the sample vessels to permit the magnet to impose a magneticinfluence on the stirrer in the respective sample vessel to move thestirrer in the respective sample vessel.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other objects, advantages and novel features of the inventionwill be more readily appreciated from the following detailed descriptionwhen read in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view of an example of a system employing animproved system and method for stirring solid samples suspended inliquid media contained in a plurality of sample vessels according to anembodiment of the present invention;

FIG. 2 is a detailed perspective view of an example of a panel in thesystem shown in FIG. 1 for housing sample vessels;

FIG. 3 is a side view of the panel shown in FIG. 2;

FIG. 4 is a diagrammatic view of a belt and pulley arrangement employedin the panel shown in FIG. 2;

FIG. 5 is a detailed perspective bottom view of the bottom two rows ofthe panel shown in FIG. 2;

FIG. 6 is a bottom view of the panel shown in FIG. 2;

FIG. 7 is a detailed exploded view of the drive arrangement of the panelshown in FIG. 2;

FIG. 8 is a detailed view of the motor of the drive arrangement shown inFIG. 7;

FIG. 9 is a conceptual view showing an example of the relationshipbetween the position and motion of a magnet in the panel show in FIG. 2and a respective sample vessel containing a stirrer in accordance withan embodiment of the present invention;

FIG. 10 is a detailed perspective view of an example of a stirrer asshown in FIG. 9;

FIG. 11 is a side view of the stirrer shown in FIG. 10; and

FIG. 12 is a cross-sectional view of the stirrer shown in FIG. 10.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

An example of an incubation and measurement module 100 employing asystem for stirring solid samples suspended in liquid media contained insample vessels 102 according to an embodiment of the present inventionis shown in FIG. 1. Further details of the system 100 and the stirringsystem are shown in FIGS. 2–9. As illustrated, the incubation andmeasurement module 100 in this example includes a housing 104 and twopanels 106 that can be slid into and out of the housing 104 alongrespective rail arrangements 108 in a direction along arrow A.

Each panel 106 includes a plurality of openings 110, each of which isadapted to receive a sample vessel 102. As discussed in more detailbelow, each vessel 102 includes a solid sample suspended in a liquidmedia, and a stirrer. The openings 110 are tilted with respect to thehorizontal so that the sample vessels 102 received in the openings 110are also tilted for reasons discussed in more detail below. In thisexample, the openings 110 are tilted at 15° or about 15° with respect tothe horizontal, so that the sample vessels 102 received in the openings110 are also tilted at 15° or about 15° with respect to the horizontal.As discussed in more detail below, this tilting creates a large air toliquid interface in the sample vessels 102. Furthermore, the openings110 and hence the sample vessels 102 need not be tilted at 15° withrespect to the horizontal, but rather, can be tilted at an angle withinthe range of at or about 15° to at or about 25°, with the range of at orabout 15° to at our about 20° being preferred. However, the openings 110and the sample vessels 102 can be tilted at any practical angle withrespect to the horizontal that will create a sufficient air to liquidinterface.

The openings 110 are arranged in a plurality of rows and columns asshown, and each panel 106 can have any practical number of openings. Forexample, the openings 110 can be arranged in ten rows and nine columns,thus totaling 90 openings 110 per panel 110. The incubation andmeasurement module 100 further includes one or more doors (not shown)for closing the housing 104 after the panels 106 have been received inthe housing 104.

When a sample culture is to be analyzed by the incubation andmeasurement module 100, the sample culture is placed in a sample vessel102, and the sample vessel 102 is loaded into a respective opening 110in a respective panel 106 in the incubation and measurement module 100.The sample vessel 102 is a closed sample vial in this example. Theincubation and measurement module 100 can further include a keyboard112, a barcode reader (not shown), or any other suitable interface thatenables a technician to enter information pertaining to the sample intoa database stored in a memory in the incubation and measurement module100, or in a computer (not shown) which is remote from the module 100and controls operation of the module 100. The information can include,for example, patient information, sample type, the row and column of theopening 110 into which the sample vessel 102 is being loaded, and so on.The module 100 can include the type of detecting devices as described inU.S. patent applications Ser. Nos. 09/892,061 and 09/892,012, referencedabove.

As further shown in FIGS. 2–8, each panel 106 includes a drive assembly114 for driving a plurality of magnet shaft assemblies 116 as describedin more detail below. The drive assembly 114 includes a drive motorassembly 118 and a pulley arrangement comprising a drive pulley 120,shaft driving pulleys 122, idler pulleys 124 and 126, and a serpentinebelt 128 that passes around the drive pulley 120, shaft driving pulleys122, and idler pulleys 124 and 126 as shown in FIG. 4. The drive motorassembly 118 includes a drive motor 130 that is controlled by, forexample, a controller 132, such as a microcontroller or the like. Thedrive shaft 134 of the drive motor 130 is coupled to a magnet plate 136as shown in detail in FIG. 8. The magnet plate 136 includes a pluralityof magnets 138, which are generally strong magnets such as rare earthmagnets. The drive motor 130 is mounted inside the housing 104 by, forexample, a mounting bracket 140.

As shown in detail in FIGS. 2 and 7, a magnet plate 142 having aplurality of strong magnets 144 such as rare earth magnets is coupled todrive pulley 120. The drive motor 130 is positioned inside housing 104so that when its corresponding panel 106 is fully inserted in thehousing 104, magnet plate 142 aligns with or substantially aligns withmagnet plate 136. It is further noted that the drive motor 130 andmagnet plate 136 are located outside of the rear wall 146 of theincubation chamber that is housed inside housing 104 and receives thepanels 106. Accordingly, as shown in FIG. 6, magnet plate 136 and magnetplate 142 are on opposite sides of the rear wall 146 of the incubationchamber. However, the magnets 138 and 144 on magnet plates 136 and 142are strong enough to magnetically couple with each other through therear wall 146 so that when the drive motor 130 rotates magnet plate 136,the magnetic coupling causes the rotation of magnet plate 136 to rotatemagnet plate 142. The rotation of magnet plate 142 drives drive pulley120, which drives the serpentine belt 128 to drive shaft driving pulleys122 and idler pulleys 124 and 126. It is noted that by locating drivemotor 130 outside of the incubation chamber, the heat emitted by drivemotor 130 during operation does not influence the temperature within theincubation chamber. Furthermore, the drive motor 130 is not influence bythe heat of the incubation chamber, which can damage the drive motor130.

As can be appreciated from FIGS. 2–7 and, in particular, FIGS. 5 and 6,each of the shaft driving pulleys 122 is coupled to a respective magnetshaft assembly 116. In this example, panel 106 includes ten shaftdriving pulleys 122 and ten corresponding magnet shaft assemblies 116,each corresponding to a respective row of openings 110. Each magnetshaft assembly 116 includes a shaft 148 that is coupled at one end to arespective shaft driving pulley 122, extends along the width of thepanel 104 and is rotatably coupled at its other end to a mountingassembly 150. A plurality of magnet assemblies 152-1 through 152-5 arecoupled to each shaft 148 and rotate in unison with the shaft 148 whenthe shaft 148 is rotated about its longitudinal axis by its respectiveshaft driving pulley 122. As shown in FIG. 5, each magnet assembly 152-1through 152-5 has one or two strong magnets 154, such as rare earthmagnets, which can be received into corresponding openings 156-1 through156-5, respectively, in the panel 106 as the shaft 148 rotates.Specifically, the total number of magnets 154 of a magnet shaft assembly116 corresponds to the number of openings 110 in the row of openingscorresponding to the magnet shaft assembly 116. In this example, magnetshaft assembly 116 includes ten magnets 154 corresponding to the tenopenings 110 in the row of openings corresponding to the magnet shaftassembly 116.

It is further noted that the magnet or magnets 154 of adjacent magnetassemblies (e.g., magnet assemblies 152-1 and 152-2) are oriented at180° or approximately 180° with respect to each other about the shaft148. That is, when the magnets 154 of magnet assembly 152-1 arepositioned outside of opening 156-1, the magnets 154 of magnet assembly152-2 are positioned inside opening 156-2 as shown in FIGS. 5 and 6. Themagnets 154 are arranged in this manner to improve the overall balanceof the magnet shaft assembly 116.

The stirring operation performed by the magnet shaft assembly 116 willnow be described. FIG. 9 shows an example of the relationship between amagnet 154 of magnet assembly 152-1 and a sample vessel 102 that hasbeen loaded into the opening 110 corresponding to the magnet 154. Asdiscussed above, each magnet 154 corresponds to an opening 110 in therow of openings corresponding to the magnet shaft assembly 116. Asshown, when a sample vessel 102 is received in an opening 110, it istilted with respect to the horizontal at the angle at which the opening110 is tilted with respect to the horizontal, which is 15° or about 15°in this example. As mentioned above, this tilting creates asignificantly large air-liquid interface in the sample vessel 102.

As further discussed above, each sample vessel 102 includes a solidsample 158, such as an organism of the type described above, that issuspended in a liquid media 160, such as a growth media for enhancinggrowth- of the organism. Each sample vessel 102 further includes astirrer 162 which is preferably a magnetic, ferrous metal filledpolymer. It is noted that the term “magnetic” in this context refers toa type of ferrous metal, such as magnetic stainless steel, that respondsto the magnetic fields of the magnet 154. The ferrous material employedin the stirrer according to this embodiment is not itself a magnet, noris it magnetized. Further details of the stirrer 162 are shown in FIGS.10–12. The stirrer 162 can be rod shaped or cylindrical as shown, orhave any other suitable shape. The stirrer 162 can have an overalllength within a range of, for example, 0.500 or about 0.500 inches to0.750 or about 0.750 inches, and can have an overall diameter of 0.120or about 0.120 inches.

The stirrer 162 can include about 50% to about 80% of polymer by weight,with the remaining 50% to 20% of the weight being ferrous metal.However, any ratio of polymer to ferrous metal can be used as long as itprovides sufficient cohesiveness to hold the stirrer 162 together and toallow sufficient responsiveness to the magnet 154. The polymer materialis preferably a biologically inert polymer, such as nylon orpolypropylene, which reduces the overall surface hardness of the stirrer162, and thus reduces potential damage to the solid sample 158 in thesuspension as well as to the sample vessel 102. The ferrous material ispreferably stainless steel, but can be any suitable material that canrespond to magnetic influence from magnet 154. The stirrer 162 can becolor coded with colors such as blue, gray, red, green, orange, and soon, to provide an indication of the type and percentage content of thepolymer and ferrous material. The stirrer 162 can be provided in thesample vessel 110, or can be added to the sample vessel 110 prior to orafter adding the solid sample 158 and liquid media 160 to the samplevessel 110.

As further shown in FIG. 9, the stirring action is created bycontrolling the motor 130 (see FIGS. 2, 3 and 5–8) to rotate the magnetshaft assembly 116 in a direction R. The rotation of the magnet shaftassembly 116 thus rotates the shaft 148 about it longitudinal axis,which in turn rotates the magnets 154 about the longitudinal axis of theshaft 148. As the magnets 154 rotate, they are brought into theirrespective openings 156-1 through 156-5 in panel 106 (see FIGS. 5 and6). That is, when shaft 148 is rotated, magnet 154 of magnet assembly152-1 cyclically enters opening 156-1 to come proximate to sample vessel102 in its corresponding opening 110, and exits opening 156-1 to becomedistant from sample vessel 102. This movement causes a rhythmicagitation of the stirrer 162 to occur. That is, as magnet 154 swipesproximate to the outer surface of sample vessel 102, its magnetic forceattracts stirrer 162 to pull stirrer 162 away from the bottom edge 164of the sample vessel 102 upward along wall 166 of the sample vessel 102.As the magnet 154 begins to rotate away from the sample vessel 102, thestirrer 162 becomes less influenced by the magnetic force of magnet 164,and due to gravity falls along wall 166 of sample vessel 102 toward thebottom edge 164. This movement is repeated each time magnet 154 swipesalong the outer surface of sample vessel 102. It is desirable for themagnet 154 to be rotated in the direction R so that the stirrer 162 isfirst moved up along wall 166 and then allowed to fall back toward thebottom edge 164. Also, the motor 130 can be rotated at a speed of, forexample, 150 rotations per minute, which causes the stirrer 162 totravel through the stirring path described above 150 times per minute.However, the motor 130 can be controlled to rotate at any practicalspeed to achieve the desired stirring action.

It is further noted that by increasing the ferrous fill content of thestirrer 162, the magnetic influence that magnet 154 has on the stirrer162 will increase. Likewise, by decreasing the ferrous fill content ofthe stirrer 162, the magnetic influence that magnet 154 has on thestirrer 162 will decrease. Accordingly, the intensity of the stirringcan be varied by simply replacing stirrer 162 with a stirrer having adifferent ferrous fill content Furthermore, the size and shape of thestirrer 162 need not be changed.

The above arrangement provides several advantages over the conventionalstirring devices discussed in the Background section above. For example,because the tilted openings 110 maintain the sample vessel 102 at ashallow angle (e.g., 15°) with respect to the horizontal to facilitatemaximum exposure of liquid phase to gas phase. This therefore providesan improved dissolved gas exchange as a function of the angle.Furthermore, the angled orientation of the sample vessel 102 increasesthe probability that the magnet 154 will maintain magnetic influenceover the stirrer 162. Also, the stirring action can be gentler than inconventional methods since the path of the stirrer 162 is constrained bythe wall 166 of the sample vessel 102. All of these improvedcharacteristics of the stirring system enhances the growth of the samplein the liquid media 160 and thus increases the overall carbon dioxideproduction, oxygen depletion and pressure variation in the sample vessel110, thereby improving sample detection results.

Table 1 below shows an example of the sample detection results obtainedby agitating various samples according to the embodiments of the presentinvention discussed above in comparison to the sample detection resultsobtained by agitating the same types of samples according to aconventional “rocking” method in which the vessel containing the sampleis agitated or rocked to thus agitate the sample therein.

TABLE 1 Sample Detection Comparison Data Magnetic Agitation RockingAgitation Time to Detection Time to Detection Organism and Strain inHours in Hours Candida glabrata 231 62 >120 Candida glabrata 550 58 >120Candida glabrata 15545 51 >120 Candida glabrata 66032 52 112 N.meningitidis 13113 47 >120 S. pneumoniae 6305 19 21

As illustrated, for each type of sample, the duration of time thatelapses from the beginning of agitation in accordance with theembodiments described above until a detectable amount of sample has beengrown is far less that the duration of time that elapses from thebeginning of the conventional “rocking” agitation technique until adetectable amount of sample has been grown. Accordingly, the agitationtechniques according to the embodiments of the invention described aboveare far superior to the conventional rocking technique.

Although only a few exemplary embodiments of the present invention havebeen described in detail above, those skilled in the art will readilyappreciate that many modifications are possible in the exemplaryembodiments without materially departing from the novel teachings andadvantages of this invention. Accordingly, all such modifications areintended to be included within the scope of this invention as defined inthe following claims.

1. A system comprising: a plurality of sample vessels, each of thesample vessels comprising a longitudinal axis, a growth medium and astirrer, the stirrer capable of being influenced by a magnetic force;and an incubation and measurement module comprising at least one panelcomprising a plurality of openings for holding the sample vessels, and amagnet driver comprising a plurality of magnets, wherein each of theopenings corresponds with one of the magnets, wherein the magnet driveris adapted to repeatedly move each magnet proximate to and distant fromthe surface of a corresponding sample vessel when located in thecorresponding opening, and wherein the openings are configured to holdthe one or more sample vessels such that the longitudinal axis of thevessels are at an angle of less than 90° with the horizontal, whereinthe magnet driver comprises: a magnet shaft assembly comprising a shaftand a plurality of magnet assemblies, wherein the plurality of magnetassemblies are coupled to the shaft, the magnet assemblies beingdiscreet components or discreet parts of a single component or acombination thereof, wherein the magnet assemblies comprise a firstmagnet coupled to and extending from the shaft at a first angle, and asecond magnet coupled to and extending from the shaft at a second angle,and wherein the first magnet corresponds with a first of the one or moreopenings and the second magnet corresponds with a second of the one ormore openings adjacent to the first of the one or more openings, whereinthe magnet shaft assembly is located in the module such that each of themagnet assemblies is located between two of the sample vessel openings.2. The system of claim 1, wherein the plurality of openings are arrangedin at least one row and at least one column.
 3. The system of claim 1,wherein the magnet driver further comprises: a motor engaged with theshaft to rotate the magnet shaft assembly and move the magnets proximateto the outer surface of the corresponding sample vessel and distant fromthe outer surface of the corresponding sample vessel.
 4. The system ofclaim 1, wherein upon operation of the magnet driver, the magneticinfluence moves the stirrer element along a side wall of the samplevessel.
 5. The system of claim 1, wherein the magnet driver and magnetsare arranged such that, during a portion of the movement of the magnets,gravity moves the stirrer element toward a bottom of the sample vessel.6. The system of claim 1, wherein the angle is about 15° to about 25°.7. The system of claim 1, wherein the sample vessels are sample vials.8. The system of claim 1, wherein the incubation and measurement modulefurther comprises a housing, and at least one door.
 9. The system ofclaim 1, wherein the magnets of adjacent magnet assemblies areorientated approximately 180° with respect to each other about theshaft.